Illicit drug use (IDU) and intimate partner violence (IPV) are important and interrelated public health issues. There is strong evidence for a cross-sectional association between IDU and IPV, but there is a shortage of research testing a longitudinal association and potential mediation/moderation effects. Leonard (1993) proposed a heuristic model of the association between substance use and IPV, whereby distal risk factors (e.g. antisocial personality, hostility) in conjunction with proximal risk factors (e.g. situational cues, psychopharmacological effects of substance use), increase the likelihood of violent events. Experimental evidence that the psychopharmacological effects of different illicit drug types (i.e. cannabis, cocaine) elicit aggressive behavior is equivocal, suggesting that it is important to research more distal effects of IDU. Previous research has speculated that IDU may increase verbal conflict in relationships, which in turn can result in a greater likelihood of IPV. A host of other variables (e.g., hostility, avoidance coping, life stress, race, antisocial personality, alcohol use and partner IDU) have been suggested as possible moderators of an association; however, there is a lack of research that directly tests these effects. This proposed study will use secondary data analysis to test a longitudinal association between IDU and IPV, and mediation\ moderation effects. To do so, data will be analyzed from the Adult Development Study (ADS), a longitudinal survey of newly married couples in Buffalo, NY. Research on IPV among newly married couples is particularly important because rates of IPV are high in this population. Couples were recruited for the ADS as they applied for their marriage license, and subsequently followed-up at their first, second, fourth, seventh and ninth wedding anniversaries. It will be important to limit the sample to the early years of marriage while retaining enough time-points to conduct meaningful longitudinal analyses; thus, data will be analyzed from the first four waves only (i.e. baseline through 4th anniversary). ADS data were collected from both spouses of 634 couples, allowing this proposed study to examine the potentially important effect of partner behaviors on relationship violence. It will be important to first examine consistency with previous findings; thus, the first specific aim of this proposed study is to test a cross-sectional relation between IDU and IPV. The second specific aim is to examine the longitudinal association between husband/wife IDU and husband/wife IPV in newly married couples. The third specific aim is to test possible mediators/moderators of an IPV-IDU association, including: a) the moderation effect of partner IDU, b) the mediation effect of verbal conflict, and c) the moderation effect of hostility, avoidance coping, life stress, antisocial personality, alcohol use, and race/ethnicity. Descriptive statistics, chi-square tests, t-tests and logistic regression will be used to examine the prevalence of IDU and IPV in the sample, and to test cross-sectional relations between IDU and IPV. Multi Level Modeling will be used to test for a longitudinal relation between IDU and IPV, as well as mediation and moderation effects.